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- Title
Fall, classification, and exposure history of the Mifflin L5 chondrite.
- Authors
Kita, Noriko T.; Welten, Kees C.; Valley, John W.; Spicuzza, Michael J.; Nakashima, Daisuke; Tenner, Travis J.; Ushikubo, Takayuki; MacPherson, Glenn J.; Welzenbach, Linda; Heck, Philipp R.; Davis, Andrew M.; Meier, Matthias M. M.; Wieler, Rainer; Caffee, Marc W.; Laubenstein, Matthias; Nishiizumi, Kunihiko
- Abstract
The Mifflin meteorite fell on the night of April 14, 2010, in southwestern Wisconsin. A bright fireball was observed throughout a wide area of the midwestern United States. The petrography, mineral compositions, and oxygen isotope ratios indicate that the meteorite is a L5 chondrite fragmental breccia with light/dark structure. The meteorite shows a low shock stage of S2, although some shock-melted veins are present. The U,Th-He age is 0.7 Ga, and the K-Ar age is 1.8 Ga, indicating that Mifflin might have been heated at the time of the 470 Ma L-chondrite parent body breakup and that U, Th-He, and K-Ar ages were partially reset. The cosmogenic radionuclide data indicate that Mifflin was exposed to cosmic rays while its radius was 30-65 cm. Assuming this exposure geometry, a cosmic-ray exposure age of 25 ± 3 Ma is calculated from cosmogenic noble gas concentrations. The low 22Ne/21Ne ratio may, however, indicate a two-stage exposure with a longer first-stage exposure at high shielding. Mifflin is unusual in having a low radiogenic gas content combined with a low shock stage and no evidence of late stage annealing; this inconsistency remains unexplained.
- Subjects
CHONDRITES; CLASSIFICATION of meteorites; BRECCIA; COSMOGENIC nuclides; RADIOISOTOPES; RADIONUCLIDE generators; NUCLEAR activation analysis
- Publication
Meteoritics & Planetary Science, 2013, Vol 48, Issue 4, p641
- ISSN
1086-9379
- Publication type
Article
- DOI
10.1111/maps.12077